Perhaps more interesting, he also noted that he's close to issuing a founder's letter 2.0. "I'm almost done writing a new letter about how I see our community and our role evolving, and I'll share it soon," he wrote.

"I had a personal obligation which meant I couldn't go," Sandberg said in an interview with Recode's Kara Swisher. "I just felt bad about not being there. So I think once I felt bad I just didn't feel comfortable posting, and I think that was a mistake. And if I had to do it again I certainly would've posted."

Life, disrupted: In Europe, millions of refugees are still searching for a safe place to settle. Tech should be part of the solution. But is it? CNET investigates.